This invention relates to medical devices, and more particularly to catheters used in minimally-invasive procedures.
Human In Vitro Fertilization (IVF) and Embryo Transfer (ET), first successfully performed in 1978, has become a widely practiced procedure to treat infertile couples who have failed with more conventional methods of therapy such as superovulation and intrauterine insemination. The most common indications for IVF and related procedures, such as Gamete In Vitro Fertilization or Gamete Intra Fallopian Transfer (GIFT) which includes women having blocked or damaged fallopian tubes, and includes low sperm and/or egg quality. Related factors include age of the female, and the degree of endometrial receptivity. The procedure may also be used in cases of severe male factor where direct (intracytoplasmic) injection of sperm is an option. Another indication for the procedure is when the shell of the egg is abnormally thick, thus preventing the fertilized and dividing early embryo to escape and implant into the uterus. Creating a small opening through the shell has been shown to increase implantation rates. IVF is also being used when clinical or genetic factors require implantation of donor eggs from a fertile female that are fertilized in vitro and implanted into the recipient female using standard techniques.
The IVF/ET procedure typically involves the hormonal stimulation of the female to first suppress her ability to ovulate on her own, then stimulate development of follicles in the ovaries with a fertility medication. The mature eggs are removed from the ovary transvaginally using a needle, preferably guided under ultrasound. Following harvesting of the eggs, the eggs are identified and sorted with regard to maturity, and then placed with a sperm sample from the male. Approximately 24 hours after fertilization, the eggs are examined to confirm fertilization, which occurs in approximately 65% to 85% of the eggs harvested. After a short development period, the embryos are transferred, along with a volume of fluid, to the uterus using a delivery catheter. The delivery catheter is made of a soft plastic material to avoid damage to the endometrium. The delivery catheter is guided to the uterus by the physician who relies on an ultrasound probe to visualize the catheter.
While improvements in the techniques and instrumentation used in this procedure have provided significant increases in pregnancy rates and births, the overall numbers still remain fairly low. Recent numbers suggest an overall pregnancy rate of around 25% with a successful outcome rate of about 22%, these numbers being somewhat higher for younger patients. There are several factors that impact on the success of the procedure including some related to the design of the delivery catheter. The functions of the delivery catheter include serving as a housing for the embryos while the catheter is navigated to the implantation site; providing a relatively atraumatic extension from the stiffer guiding catheter for delivery; and serving as a conduit for injecting the fluid containing embryos into the endometrial cavity for implantation. Complications can include inadvertent flushing of the eggs into the fallopian tube, or suctioning the eggs out as the catheter is withdrawn. Visualization of the catheter can be another problem. Since ultrasound is two dimensional, the catheter can only be distinguished when it is relatively perpendicular with respect to the probe. When the catheter is angled, the reflected waves often do not return to the probe and visibility is lost. Because of the soft nature of the standard delivery catheter, in a number of cases, the tip of the catheter may bend back on itself or curve away from the fundus of the uterus. The tip may also accidently pass between the layer of the endometrium and myometrium. Misdirection of the catheter tip can be difficult to see under ultrasound and, if not corrected, usually results in lack of implantation and fertilization. Conversely, a stiffer catheter increases the risk of trauma to the uterus or cervix, with the latter possibly leading to the release of prostaglandins and expulsion of the eggs from the endometrium.
Another factor to be considered with respect to conventional IVF/ET procedures is that the cost of the procedure in conjunction with resulting relatively low pregnancy rates compels the delivery of multiple embryos during each procedure to increase the chance of at least one successful implantation. Often, unwanted multiple births result from this practice. If a higher pregnancy rate could be achieved, the need for multiple embryo implantation would be lessened or eliminated.
With the high cost of IVF and pregnancy rates that are still under 50%, what is needed is a soft-tipped catheter that can increase the likelihood of successful embryo implantation in a majority of the patients desiring this procedure. Ideally, the physician should be able to safely and accurately place the catheter at the implant site to deliver an optimal combination of fluid and embryos, resulting in successful implantation and birth of a healthy newborn.
The foregoing problems are solved and a technical advance is achieved in an illustrative transfer or delivery catheter which includes ultrasonically reflective components or features to enhance its visibility under transabdominal or transvaginal ultrasound guidance, during ET, for example. An exemplary embodiment of the invention includes coaxial catheter apparatus including an outer guide catheter and an inner transfer or delivery catheter. The guide catheter is preferably constructed of a relatively stiff material such as polytetrafluoroethylene (PTFE) and the transfer or delivery catheter is preferably constructed of a second material having a lower durometer such as polyethylene, urethane, polyolefin, amides, or silicone. The delivery catheter has a greater flexibility than the guide catheter, and that flexibility is achieved either by use of a lower durometer material or by shaping the delivery catheter so that it uses the same material as the guide catheter but is more flexible. In such a case, the external diameter of the delivery catheter will be less than that of the guide catheter. Ultrasonically detectable feature(s) is/are incorporated in the distal region of the transfer or delivery catheter, such as a band that is attached over the transfer or delivery catheter. The ultrasonically detectable feature or features may include, for example, an area or areas with reflectivity differing from that of the neighboring parts. The differing reflectivity may be greater or less than that of the neighboring parts. Ultrasonically detectable feature or features may also be incorporated adjacent the distal tip of the guiding catheter.
The catheter apparatus may alternately comprise a single piece comprising a stiffened proximal component or portion or a reinforcement component or member, as an outer or inner tube or cannula
Where the catheter is used for embryo transfer, the diameter of the passageway through the transfer catheter is preferably no greater than 0.025xe2x80x3, and most preferably between 0.018xe2x80x3 and 0.021xe2x80x3. Such a diameter would permit a transfer volume (the volume of fluid and material including at least one gamete, blastocyst or zygote) less than 30 xcexcl and most preferably between 5 and 15 xcexcl.